RESUMEN
Schistosomes are pathogenic helminth parasites of human portal veins. Their body wall is a highly active syncytial tegument involved in an array of host interactions. The cytoskeletal organization and dynamics of this syncytium are poorly understood, but predominant motor components are the LC8 class of cytoplasmic dynein light chains (DLC). Four LC8 members occur in schistosomes, two of which are expressed in the tegument. Here, we describe the cytoplasmic distribution, stage-specific expression and cellular location of two diverse LC8 molecules of Schistosoma japonicum. SjDLC1 was detected in surface-membrane specific extracts of adult worms and was shown by quantitative immuno-electron microscopy to predominate along heptalaminate membranes of the worm surface. SjDLC3 also occurs in the tegument, but was shown to be present in basal layers of the tegument and did not preferentially co-localize with particular membrane components. SjDLC3 was also detected in the gastrodermis. SjDLC1 is expressed only in mammalian-parasitic stages, whereas SjDLC3 is expressed throughout the life-cycle. The data suggest that SjDLC1 is preferentially located to the host-interactive distal parasite membrane, and plays a role in surface membrane dynamics, while SjDLC3 is a ubiquitous motor component of schistosome epithelia of all stages.
Asunto(s)
Dineínas/metabolismo , Células Gigantes/metabolismo , Proteínas del Helminto/metabolismo , Schistosoma japonicum/metabolismo , Animales , Membrana Celular/metabolismo , Dineínas/química , Dineínas/genética , Electroforesis en Gel Bidimensional , Proteínas del Helminto/química , Proteínas del Helminto/genética , Humanos , Microscopía Inmunoelectrónica , Modelos Moleculares , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Schistosoma japonicum/ultraestructuraRESUMEN
Disrupting the binding interaction between proprotein convertase (PCSK9) and the epidermal growth factor-like domain A (EGF-A domain) in the low-density lipoprotein receptor (LDL-R) is a promising strategy to promote LDL-R recycling and thereby lower circulating cholesterol levels. In this study, truncated 26 amino acid EGF-A analogs were designed and synthesized, and their structures were analyzed in solution and in complex with PCSK9. The most potent peptide had an increased binding affinity for PCSK9 (KD = 0.6 µM) compared with wild-type EGF-A (KD = 1.2 µM), and the ability to increase LDL-R recycling in the presence of PCSK9 in a cell-based assay.
Asunto(s)
Péptidos/metabolismo , Proproteína Convertasas/metabolismo , Receptores de LDL/metabolismo , Serina Endopeptidasas/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Línea Celular , Colesterol/metabolismo , Factor de Crecimiento Epidérmico/química , Transferencia Resonante de Energía de Fluorescencia , Humanos , Simulación de Dinámica Molecular , Datos de Secuencia Molecular , Mutagénesis , Péptidos/síntesis química , Péptidos/química , Proproteína Convertasa 9 , Proproteína Convertasas/química , Proproteína Convertasas/genética , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Serina Endopeptidasas/química , Serina Endopeptidasas/genéticaRESUMEN
Schistosomes are parasitic blood flukes, responsible for significant human disease in tropical and developing nations. Here we review information on the organization of the cytoskeleton and associated motor proteins of schistosomes, with particular reference to the organization of the syncytial tegument, a unique cellular adaptation of these and other neodermatan flatworms. Extensive EST databases show that the molecular constituents of the cytoskeleton and associated molecular systems are likely to be similar to those of other eukaryotes, although there are potentially some molecules unique to schistosomes and platyhelminths. The biology of some components, particular those contributing to host-parasite interactions as well as chemotherapy and immunotherapy are discussed. Unresolved questions in relation to the structure and function of the tegument relate to dynamic organization of the syncytial layer.